Electromagnetic brake



' Feb. 20, 1940. ER 2,191,188

ELECTROMAGNETI C BRAKE Original Filed Dec. 20, 1937 IAN/EH70)? NORRIS B URR Gil/"185 RS BY A TTORNEY Patented Feb. 20, 1940 2,191,188

ELECTROMAGNETIC BRAKE Morris Burr Chambers, San Francisco, Calif.

Application December 20, 1937, Serial No. 180,817 Renewed June 29, 1939 7 Claims. (Cl. 188-438) This invention relates generally to brakes and, of radially extending arms, the structure and purmore particularly, to electromagnetic brakes of poses ofwhich will presentlybe set forth. This the type disclosed in my Patent No. 2,024,847, Despider affords spaces or openings between the cember 17, 1935. In fact, the present invention arms for ventilation. When applied to relatively I is, in some ways, an improvement on the brake light vehicles, the operation of the brake does not of that patent. In that brake, thecam which op result in the generation of great heat, and a conerates between the brake shoes is pivoted upon tinuous plate or disk can be used. But if it be and turns about a pin which projects from the applied to a heavy vehicle, particularly one with back plate. Necessarily, the cam swings in an a heavy trailer attached to it, the heat generated D are which extends not only laterally from the cenby the brake becomes very great and ventilation is tral or neutral position of the cam but inwardly desirable. The drawing shows the brake adapted or away from the rim or braking flange of the for this heavy duty.

brake-drum. Since, while moving in this inward Surrounding the spider l, and partially hously directed arc, the cam is in contact with one or ing it, is the braking flange H of the brake drum,

the other. of the brake-shoes, it has a tendency the vertical web of the drum being indicated, in 1'5 to draw the contacted shoe inwardlyand thus to part,.at Hi. This web is attached to the wheel move it away from the flange of the drum, thereto be braked, as is well understood. Within the by retarding the braking action. and requiring braking flange I3 is the brake band Md and its more power to start it. One of the objects of my lining iii. The band is split at the top of the UV present invention is to eliminate, as far as is pracdrum, and to its ends are applied-brake-shoes i6 ticable, this tendency to draw the brake-shoe inand H. i As shown, the shoe it is attached. rigidly wardly at the very instant that it should be movand directly to the respective end of the band, ing the brakeband into contact with the drum while the shoe i1 is adjustably attached to the flange. 3 other end and is adapted for limited movement 5 In the accompanying drawjng I have shown On. the band 85 thebrake lining wears. Various three specific structures for attaining the above structures could be used to efi'ect this adjustment. stated and other objects. Other practicable That shown comprises members Na and llb which structures therefor may be employed and I desire are fixed to the band with a space We between it to be understood that the claims hereof are not t em- The member 47b isin the form of a tllbw 0 intended to be limited to the details of structure lar sleeve into which extends and slidingly fits. a

disclosed any farther than. their specific terms projection 0n t Shoe This p le iorrhas a require. 1 threaded socket open at the end toward the mem In said drawing, Fig. 1 is a view taken vertically 1061 Ha for an adjusting SCFEW bolt the through the brake-drum inside the wear plate for latter having a suitably shapedwren h ns s s 5 the magnet, as on line l--l of 6; Fig. 2 .isa enlargement in the space l'lc. By turning the vertical sectional view through. the brake-shoes screw or bolt l'ld, the shoe H is moved with reand the upper part of the magnet lever, showing spect to the brake band and wear is thus takcn up.

the structure at the upper part of Fig. 1; Figrl is A similar adjusting devicemay, if'desir cd, be ema section on line 33 of Fig. 2; Fig. 4 is a side ployed for the shoe l8. It is assumed that, when elevation of a modified form of brake shoes and the vehicle is moving forwardly, the wheel and it UNITED STATES PATENT OFFICE 0 magnet lever; Fig. 5 is a view similar to Fig. 4 but brake drum turn toward the r clockwise, 40

showing another modification; Fig. 6 is a vertical as viewed in Fig. 1. To brake the drum when it section through the lower part of the brake-drum, is turning that irection, the brake-shoe ll as on line 6-45 of Fig.1, and Fig. 7 is a section on is moved to the right, whereupon the right-hand line 'l.-'l of Fig.1. part of the band lining is gripped by the drum Referring first to Fig. 6, it represents a portion fl e and the drum is broughtto. rest. At the of the axle structure of a vehicle to which my insame time, the shoe It is but lightly applied and vention is applied. Bolted, or otherwise secured t e e s little WQ f the brake lining at at d to said axle structure is aback member ll; correof the brake. When the wheel and drum are D spending to the usual back-plate of the brake r n kw y. it is the e l5 which is 01 drum. In the present case, however, this memcrated in b aking and ill is the lining at and t0 the her is in the form of a spider, having a ring-like left of that shoe that is subjected to wear. Howportion through which bolts l2 are passed to seever, the. vehicle is movingbackwardly so little cure it to the axle structure. The ring-like porof the time that this wear is almost negligible. tion of the member H is provided with a plurality For that reason, the shoe I6 is not adjustably tween that shoe and the anchor is will seize the v drum flange and be active in braking. Preferably about 240 of the band or lining is thus seized. The other anchor is shown at 22. It, too, is rigidly attached to the band [4a and is adapted to act against another arm 23 on the spider H. This arm, however, has an eccentrically mounted con-. tact pin 24 which is positioned for engagement with an arcuatesurface formed in the anchor 22.

' By turning the contact pin more or less in one directionor the other, the anchor 22 and the band .is moved toward or from the brake flange 13 to take up wear of the lining. Preferably the point of anchorage at 22 is 240 from. the end of shoe l 6. At its lower part, the spider has another arm, 25 (see Fig. 6), which carries an eccentrically mounted disk 23 for engagementwith the band l4a, thus to take up wear of the brake-band lin- Y ing at that point. The perimeter of this disk extends between a pair of ribs 2! on the band to hold the latter against possible lateral movement. Arms 28 and 29, which project upwardly from the ring-like portion H of the spider, have pins 30 I and 3 1, respectively, for holding the band l4 outwardly at its upper ends.

attached to the spider H and to the band Ma.

near the arms is and 23 return the band to its normal or unbraking position after operation.

I as.

The brake shoes are moved by a relatively short finger or member 33 which projects upwardly between them. This finger is part of an operating lever which has a pairof arms 34 and 35 that extend in opposite direction from the finger and curve about the axis of the drum, their lower ends approaching each other to support an electromagnet 36. As best seen in Fig. 6, this magnet faces an armature ring or plate 3'! which is rigidly mounted on the inner side of the drum web [4 and, of course, rotates with it. This part of the invention is very nearly the same as is shown and described in my said Patent No.

2,024,847 and its operation is the same, so that it is deemed unnecessary to enter into a more detailed description herein. Means, fully disclosed in said patent, are provided for supplying current to v the magnet36 when the brake is to be operated. Upon energization of said magnet;

the rotating armature plate is seized magnetically and the magnet is swung tothe left or right, as the case may be. In so swinging, the lever which carries the magnet is also swung and the finger 33 is caused to push one or the other of the brake shoes away from its normal position and thus set the brake at that end of the band to which the displaced shoe is attached.

The salient feature of my present invention resides in the means for supporting the magnet lever and the finger 33 thereof. In-my former patent,"this support comprised a pivot pin which was projected inwardly from the back plate. There was but one objection to that structure and it was not serious. However, it was what led me to my present invention. When the lever of the patent is swung, the cam between the Springs 32, which are brake shoes moves in an are about the said pivot pin. The highest point of this are is at the top of the drum at the center of the cam. On both has now been overcome by the elimination of the pin as a pivotal support and by supporting the lever on the brake shoes themselves.

Taking upthe structure which is illustrated in Figs. 1, 2 and 3, the facing ends of the shoes are, each provided with a recess 38 and the finger 33 with a pairof oppositely positioned lugs 39 which extend into the respective recesses, as best seen in Figs. '2 and 3. In assembling, the band I4 is sprung open, the finger is inserted between its ends, and the band is then permitted to close upon the finger. The lugs 39 are caught within the recesses and cannot escape from them when the brake band is assembled within the drum.

Therefore, the finger, the lever and the electro- In so doing, the finger fulcrums against the shoe I 6 at point 40. Pressure at that point moves theshoe l6 backwardly and also upwardly. The

fulcrum point is not fixed but yields in an outward direction. This tendency to yield outwardly is contributed to by the resistance of shoe I! to upward movement since it is held outwardly by the guide lug 3| on the arm 29. As the outer end of the finger moves to the right, therefore, the fulcrum point 40 moves outwardly with the result that the point 4| of contact with the shoe I! moves almost horizontally and pushes shoe I! to the right without'rnoving it away from the drum flange.

the point 40a and presses against shoe H5 at the point 4 Ia. It will thus be seen. that the lever 3435 has no fixed pivot but floats with the movements of the brake shoes.

In Fig. 5 I have shown a structure like that of Fig. 2 except that the recesses 42 in thefaces of the shoes extend entirely across said'faces,

and the lugs 43 are as thick as the finger. such structure it would be possible for the finger 44 to move laterally. To prevent lateral movement thereof, I extend a pin 45 forwardly, preferably from the spider ring H, through an elongated slot 46 in the finger and lugs 43 and apply,

a washer 41 and cotter pin 48. The finger 44 floats with-the brake shoes, as in Fig. 3 and moves slot when the operating lever is swung in either direction.

In the structure shown in Fig. 4, the face or one of the shoes (l6, as shown), is cut away at If and when the finger 33 be moved in the opposite direction, it fulcrums at its upper part to form a shoulder 49. The other 49 and the lever is supported by that shoulder.

That is to say, the weight of the lever and the magnet is carried by the shoulder on the one shoe l B. To prevent the shoefrom sagging due to the weight, a pin or lug 52 is projected from a stationary part of the structure and the shoe l6 rests on it. The action of the finger 5| upon the brake shoes is similar to that of fingers 33 and 44 and need not be described indetail further than to point out that the bearing point 53 on the shoe I1 is substantially above the fulcrum point 54 on the shoe l6. When the finger turns to the right about this fulcrum the point 53 moves almost horizontally and there is substantially no tendency to move the shoe I1 away from the drum flange.

Having described my invention, I claim:

1. In an electromagnetic brake,arotatable drum having a braking surface, a non -rotatable member, a split brake-band anchored intermediate its ends to said member and adapted to be brought into contact with said braking surface, a

shoe for and attached to each end of said band,

the shoes facing each other at their adjacent ends and each of said facing ends being provided with a recess, a lever mounted for rocking movement within the brake-drum and having a finger projecting between the facing ends of said shoes, a pair of lugs on the opposite. faces of said finger, said lugs extending into the respective recesses in the brake shoes when the brake is assembled, whereby the lever is supported from the said shoes, an electromagnet mounted on said lever and an armature turningwith the drum and positioned for magnetic engagement by the electromagnet when the latter is energized, for the purpose specified.

2. An electromagnetic brake as set forth in claim 1 in which the drum is provided with a flange and in which the braking surface is the interior surface of said flange.

3. An electromagnetic brake as set forth in claim 1 in which the recesses in the facing ends of the brake shoes are closed at their sides to provide means for engaging the sides of the lugs on the finger, thus to hold the finger and the magnet lever from sidewise movement.

4. An electromagnetic brake as set forth in claim 1 in which the bottoms of the recesses in the brake shoes are rounded and the lugs on said finger are correspondingly rounded to fit within the said recesses.

5. An electromagnetic brake as set forth in claim 1 having means for adjusting one of the shoes with respect to the brake-band to take up wear.

6. A brake comprising a rotatable drum hav ing an inner braking surface; a nonrotatable member, a split brake-band having an outer lining anchored intermediate its ends to said member and extending about within said drum in proximity to the braking surface thereof, a brake manually-controlled means for swinging said lever to cause the finger thereon to move one of the said shoes thus to cause the brake-band lining to engage the said inner braking surface.

'7. A brake as set forth in claim 6 in which a stationary member is provided below that shoe which has the notch extending inwardly, said.

member being adapted to prevent the brake-band from sagging under the weight of the lever.

MORRIS BURR CHAMBERS. 

